Public domain data

These data have no specific confidentiality restrictions for users. However, users must acknowledge data sources as it is not ethical to publish data without proper attribution. Any publication or other output resulting from usage of the data should include an acknowledgment.

The recommended acknowledgment is

"This study uses data from the data source/organisation/programme, provided by the British Oceanographic Data Centre and funded by the funding body."

Sea Bird Electronics SBE13 Dissolved Oxygen Sensor

The SBE 13 was designed as an auxiliary sensor for Sea Bird SBE 9plus, but can fitted in custom instrumentation applications. When used with the SBE 9 Underwater Unit, a flow-through plenum improves the data quality, as the pumping water over the sensor membrane reduces the errors caused by oxygen depletion during the periods of slow or intermittent flushing and also reduces exposure to biofouling.

The output voltage is proportional to membrane current (oxygen current) and to the sensor element's membrane temperature (oxygen temperature), which is used for internal temperature compensation.

Two versions of the SBE 13 are available: the SBE 13Y uses a YSI polarographic element with replaceable membranes to provide in situ measurements up to 2000 m depth and the SBE 13B uses a Beckman polarographic element to provide in situ measurements up to 10500 m depth, depending on the sensor casing. This sensor includes a replaceable sealed electrolyte membrane cartridge.

The SBE 13 instrument has been out of production since 2001 and has been superseded by the SBE 43.

Sea-Bird Electronics SBE 911 and SBE 917 series CTD profilers

The SBE 911 and SBE 917 series of conductivity-temperature-depth (CTD) units are used to collect hydrographic profiles, including temperature, conductivity and pressure as standard. Each profiler consists of an underwater unit and deck unit or SEARAM. Auxiliary sensors, such as fluorometers, dissolved oxygen sensors and transmissometers, and carousel water samplers are commonly added to the underwater unit.

Underwater unit

The CTD underwater unit (SBE 9 or SBE 9 plus) comprises a protective cage (usually with a carousel water sampler), including a main pressure housing containing power supplies, acquisition electronics, telemetry circuitry, and a suite of modular sensors. The original SBE 9 incorporated Sea-Bird's standard modular SBE 3 temperature sensor and SBE 4 conductivity sensor, and a Paroscientific Digiquartz pressure sensor. The conductivity cell was connected to a pump-fed plastic tubing circuit that could include auxiliary sensors. Each SBE 9 unit was custom built to individual specification. The SBE 9 was replaced in 1997 by an off-the-shelf version, termed the SBE 9 plus, that incorporated the SBE 3 plus (or SBE 3P) temperature sensor, SBE 4C conductivity sensor and a Paroscientific Digiquartz pressure sensor. Sensors could be connected to a pump-fed plastic tubing circuit or stand-alone.

Temperature, conductivity and pressure sensors

The conductivity, temperature, and pressure sensors supplied with Sea-Bird CTD systems have outputs in the form of variable frequencies, which are measured using high-speed parallel counters. The resulting count totals are converted to numeric representations of the original frequencies, which bear a direct relationship to temperature, conductivity or pressure. Sampling frequencies for these sensors are typically set at 24 Hz.

The temperature sensing element is a glass-coated thermistor bead, pressure-protected inside a stainless steel tube, while the conductivity sensing element is a cylindrical, flow-through, borosilicate glass cell with three internal platinum electrodes. Thermistor resistance or conductivity cell resistance, respectively, is the controlling element in an optimized Wien Bridge oscillator circuit, which produces a frequency output that can be converted to a temperature or conductivity reading. These sensors are available with depth ratings of 6800 m (aluminium housing) or 10500 m (titanium housing). The Paroscientific Digiquartz pressure sensor comprises a quartz crystal resonator that responds to pressure-induced stress, and temperature is measured for thermal compensation of the calculated pressure.

Additional sensors

Optional sensors for dissolved oxygen, pH, light transmission, fluorescence and others do not require the very high levels of resolution needed in the primary CTD channels, nor do these sensors generally offer variable frequency outputs. Accordingly, signals from the auxiliary sensors are acquired using a conventional voltage-input multiplexed A/D converter (optional). Some Sea-Bird CTDs use a strain gauge pressure sensor (Senso-Metrics) in which case their pressure output data is in the same form as that from the auxiliary sensors as described above.

Deck unit or SEARAM

Each underwater unit is connected to a power supply and data logging system: the SBE 11 (or SBE 11 plus) deck unit allows real-time interfacing between the deck and the underwater unit via a conductive wire, while the submersible SBE 17 (or SBE 17 plus) SEARAM plugs directly into the underwater unit and data are downloaded on recovery of the CTD. The combination of SBE 9 and SBE 17 or SBE 11 are termed SBE 917 or SBE 911, respectively, while the combinations of SBE 9 plus and SBE 17 plus or SBE 11 plus are termed SBE 917 plus or SBE 911 plus.

SeaTech fluorometer S131

This fluorometer is designed to measure in situ chlorophyll-a fluorescence and provide high resolution data for assessment of phytoplankton biomass and monitoring of primary productivity in fresh or marine waters. It's versatility allows the instrument to be deployed on a mooring or in profiling mode. It is not sensitive to ambient light, permitting laboratory calibration with normal room lighting, and field measurements to be made at the water surface.

RV Cirolana 23/2002 CTD Data Documentation

Instrumentation

The instrument used for casts 1-19, 24-30 and 35-66 was a Sea-Bird SBE911 plus.

Details of the sensors on the CTD are -

Manufacturer

Sensor

Serial No.

Manufacturer Cal. Date

Sensor Units

Sea-Bird

Pressure

64240

26 Oct 2000

Decibars

Sea-Bird

Temperature

2041

19 Oct 2000

Centigrade

Sea-Bird

Conductivity

1615

19 Oct 2000

Siemens/meter

Sea-Bird

Oxygen

130411

28 Feb 1996

cm3/dm3

Sea-Tech

Fluorometer

131S

01 Apr 1998

Volts

Sea-Tech

Transmissometer

238D

02 Aug 1996

Volts

The instrument used for casts 20-23 and 31-34 was a Sea-Bird SBE25 Sealogger.

Details of the sensors on the CTD are -

Manufacturer

Sensor

Serial No.

Manufacturer Cal. Date

Sensor Units

Sea-Bird

Pressure

051128

13 May 2000

Decibars

Sea-Bird

Temperature

1696

13 May 2000

Centigrade

Sea-Bird

Conductivity

1454

13 May 2000

Siemens/meter

Sea-Tech

Fluorometer

131S

01 Apr 1998

Volts

Sea-Tech

Transmissometer

238D

02 Aug 1996

Volts

Calibrations

The calibrations for casts 1-19, 24-30 and 35-66 were as follows:

Parameter

Value of m (y=mx+c)

Value of c (y=mx+c)

Equation

Pressure

1.000000

0.000000

P(cal) = P(obs)

Temperature

1.000000

0.000000

T(cal) = T(obs)

Conductivity

1.000169

-0.002970

C(cal) = 1.000169C(obs) + -0.002970

Oxygen

1.000000

0.000000

O(cal) = O(obs)

Oxygen Saturation

1.000000

0.000000

OS(cal) = Os(obs)

Fluorescence

0.000244

0.065469

Chlor.(cal)(ug/l) = 0.000244F(obs)(V) + 0.065469

Beam Attenuation

1.000000

0.000000

B(cal) = B(obs)

The calibrations for casts 20-23 and 31-34 were as follows:

Parameter

Value of m (y=mx+c)

Value of c (y=mx+c)

Equation

Pressure

1.000000

0.000000

P(cal) = P(obs)

Temperature

1.000000

0.000000

T(cal) = T(obs)

Conductivity

0.999239

0.035327

C(cal) = 0.999239C(obs) + 0.035327

Fluorescence

0.000244

0.065469

Chlor.(cal)(ug/l) = 0.000244F(obs)(V) + 0.065469

Beam Attenuation

1.000000

0.000000

B(cal) = B(obs)

Data Quality Information

These data appear to be good.

General Data Screening carried out by BODC

BODC screen both the series header qualifying information and the parameter values in the data cycles themselves.

Header information is inspected for:

Irregularities such as unfeasible values

Inconsistencies between related information, for example:

Times for instrument deployment and for start/end of data series

Length of record and the number of data cycles/cycle interval

Parameters expected and the parameters actually present in the data cycles

Originator's comments on meter/mooring performance and data quality

Documents are written by BODC highlighting irregularities which cannot be resolved.

Data cycles are inspected using time or depth series plots of all parameters. Currents are additionally inspected using vector scatter plots and time series plots of North and East velocity components. These presentations undergo intrinsic and extrinsic screening to detect infeasible values within the data cycles themselves and inconsistencies as seen when comparing characteristics of adjacent data sets displaced with respect to depth, position or time. Values suspected of being of non-oceanographic origin may be tagged with the BODC flag denoting suspect value; the data values will not be altered.

The following types of irregularity, each relying on visual detection in the plot, are amongst those which may be flagged as suspect:

If a large percentage of the data is affected by irregularities then a Problem Report will be written rather than flagging the individual suspect values. Problem Reports are also used to highlight irregularities seen in the graphical data presentations.

Inconsistencies between the characteristics of the data set and those of its neighbours are sought and, where necessary, documented. This covers inconsistencies such as the following:

Maximum and minimum values of parameters (spikes excluded).

The occurrence of meteorological events.

This intrinsic and extrinsic screening of the parameter values seeks to confirm the qualifying information and the source laboratory's comments on the series. In screening and collating information, every care is taken to ensure that errors of BODC making are not introduced.

Fixed Station Information

Station Name

Nolso - Flugga Line

Category

Offshore route/traverse

Nolso-Flugga - Faroe-Shetland Channel section

Long term monitoring carried out by the Marine Laboratory Aberdeen began in the early 1890's by the forerunner of the laboratory, the Fishery Board of Scotland (est. 1882). The first water bottle casts were carried out during 1893 and conducted by Dr H N Dickson on board HMS Jackal. Four of these stations were to become part of the now standard Nolso-Flugga Faroe-Shetland Channel section. In addition, at positions further south, he sampled at three stations and these were to become part of the standard Fair Isle-Munken section. A full set of stations (12) were first sampled along the Nolso-Flugga line in 1903, and since then have more or less been sampled annually or more except for the war years. Since then extra stations have been added to both sections.

Map of standard stations

Nolso-Flugga stations

Listed below are details of the standard hydrographic stations that form the Nolso-Flugga line.

Related series for this Fixed Station are presented in the table below. Further information can be found by following the appropriate links.

If you are interested in these series, please be aware we offer a multiple file download service. Should your credentials be insufficient for automatic download, the service also offers a referral to our Enquiries Officer who may be able to negotiate access.